(1) Field of the Invention
This invention relates to apparatus and methods for decoding a bit stream using synchronization information contained in two synchronization marks embedded in the bit stream and more particularly to the capability of using the synchronization information in either of the synchronization marks.
(2) Description of the Related Art
When data is retrieved from a storage media the beginning and end of the data stream must be correctly determined. This is accomplished using synchronization data contained in two synchronization marks. If the separation between the first and second synchronization marks is large there is a possibility that large amounts of data can be lost if there is a failure in decoding the first synchronization mark.
U.S. Pat. No. 5,796,690 to Kanno describes a disc controller with improved data sync and re-sync mark detection. In response to sync and re-sync mark detection failure status signals, a re-sync mark detection window expands a timing window opening to improve the possibility of detection of the next re-sync mark.
U.S. Pat. No. 5,844,920 to Zook et al. describes a method for thermal asperity compensation using multiple sync marks for retroactive and split segment data synchronization in a magnetic disk storage system. In a magnetic disk storage system, byte synchronization to sector data is achieved even when noise in the read channel, due for instance to a thermal asperity (TA), corrupts the primary preamble and/or sync mark fields or causes a loss of frequency or phase lock. The data sector format is modified to comprise at least one secondary sync mark in addition to the conventional primary sync mark recorded at the beginning of the data field. In this manner, when the primary sync mark becomes undetectable due to errors, or when byte synchronization is lost, the storage system can still synchronize to the data sector using the secondary sync mark.
U.S. Pat. No. 6,009,549 to Bliss et al. describes a disk storage system employing error detection and correction of channel coded data, interpolated timing recovery, and retroactive and split-segment symbol synchronization. The disk storage system allows retroactive and split-segment symbol synchronization using multiple sync marks.